[asterisk-bugs] [JIRA] (ASTERISK-24521) [patch] Segfault due to null pointer in ast_bridged_channel

[Matt Jordan (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-24521?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=224172#comment-224172 ] 

Matt Jordan commented on ASTERISK-24521:
----------------------------------------

Are you sure you are running an unmodified version of Asterisk?

{{ast_channel_tech}} should *never* return NULL. It is set to a 'fake tech' before a channel is linked into the channels container to prevent this. Channel technologies are static, immutable structures, and are never removed from a channel. Grepping through the source for {{ast_channel_tech_set}} shows that it is never set to NULL.

Your check should never be needed, as {{ast_channel_tech(bridged)}} should - in an unmodified version of Asterisk - always return a valid pointer.

> [patch] Segfault due to null pointer in ast_bridged_channel
> -----------------------------------------------------------
>
>                 Key: ASTERISK-24521
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-24521
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Core/Channels
>    Affects Versions: 11.8.1
>            Reporter: Ben Smithurst
>         Attachments: ast_bridged_channel.diff, backtrace.txt
>
>
> We have observed a crash in ast_bridged_channel due to a null pointer.  We do not know at present how to reproduce it, it is something we haven't really seen before but then saw several times in a single day.
> The cause appears to be a bridged channel existing without a 'tech' field, so the ast_bridged_channel function dereferences a null pointer, the fix is quite simple and seems to work for us, we've seen no further occurences of the crash.
> *Hopefully* I still have the backtrace/core file, but if not, as I say we don't know how to reproduce it, apologies.



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